1. Field of Invention
This invention relates to a process for the production of a titanium trichloride catalyst and a process for the polymerization of .alpha.-olefins using this catalyst and, more particularly, it is concerned with an improved process for producing a titanium trichloride catalyst by treating a reduced solids product, obtained by reducing titanium tetrachloride with an alkylaluminum halide composition at low temperature, with a dialkyl ether and hexachloroethane, and a process for using the resulting catalyst as a co-catalyst with an organo-metal compound for the polymerization of .alpha.-olefins.
2. Discussion of Prior Art
Several methods have recently been described in the published patent literature which relate to preparation of titanium trichloride compositions. Generally, these methods include treating a reduced solids product, obtained by low temperature reduction of titanium tetrachloride with an organo aluminum compound, with complexing agents and with various halogenated compounds to obtain titanium trichloride catalyst compositions useful as a co-catalyst with an organo-metal compound for the polymerization of .alpha.-olefins.
More particularly, in Japanese Patent Application (OPI) No. 34478/1972 (published on Nov. 21, 1972, corresponding to British Pat. No. 1,391,068) a process is described which comprises treating such reduced solids product with a complexing agent, e.g., an ether, and titanium tetrachloride. However, as disclosed, this method requires the use of titanium tetrachloride at relatively high concentrations to produce catalytic complexes comprising TiCl.sub.3 having high activity and very good stereospecificity in polymerization of .alpha.-olefins.
In Japanese Patent Application (OPI) No. 112289/1975 (published on Sept. 3, 1975), there is described a process wherein such titanium trichloride-containing reduced solids product is treated with a complexing agent, e.g., ethers, and then the resulting brown TiCl.sub.3 -containing catalyst is treated with carbon tetrachloride. Additionally, in Japanese Patent Application (OPI) No. 143790/1975 (published on Nov. 19, 1975) a method is described comprising treating such reduced solids product with a mixture of a complexing agent and carbon tetrachloride.
In Japanese Patent Application (OPI) No. 149897/1976 (published on Dec. 23, 1976, corresponding British Pat. No. 1,484,086) a process for the preparation of violet TiCl.sub.3 is described in which a brown titanium trichloride, obtained by the above-mentioned low temperature reduction of TiCl.sub.4 with an organo aluminum halide, is subjected to a heating treatment in the presence of a halogenated aliphatic or aromatic hydrocarbon. It is further disclosed that the brown titanium trichloride obtained by the reduction step may be treated with a complexing agent, including ethers, prior to the heating treatment in the presence of the halogenated aliphatic or aromatic hydrocarbon.
In Japanese Patent Application (OPI) No. 227/1977 (published on Jan. 5, 1977) a process is disclosed which comprises heat-treating the reduced solid, treating it with a complexing agent and then treating the resulting solids with an alkylaluminum dihalide or titanium tetrachloride or a reagent capable of forming titanium tetrachloride in situ such as, for example, carbon tetrachloride.
Furthermore, in U.S. Pat. No. 3,825,524, there is disclosed a process for producing a titanium trichloride catalyst having high activity which includes extracting a crude titanium trichloride composition, obtained by reducing titanium tetrachloride with an organoaluminum chloride, with a mixed solvent system composed of (i) a main solvent of aliphatic or aromatic hydrocarbons, aromatic chlorinated hydrocarbons or trichloroethylene, and (ii) an auxilliary solvent, including ethers.
The inventors have already proposed, in parent U.S. application Ser. No. 774,964, now abandoned, a process for the production of a titanium trichloride catalyst complex capable of exhibiting very excellent catalytic performances in the polymerization of .alpha.-olefins in the presence of an organo metal compound, for example, in respect of polymerization activity, stereoregular properties and particle properties of the resultant polymer particles. Parent application Ser. No. 774,964, now abandoned, which is incorporated herein by reference as if copied in full, describes and claims a process which comprises reducing titanium tetrachloride with an organoaluminum halide compound at low temperature and then treating at elevated temperature the resulting reduced solids product with a chlorinated saturated hydrocarbon having two carbon atoms in the presence of an ether complexing agent.
The inventors have made further studies in detail on this method and consequently have found that a titanium trichloride catalyst showing surprisingly excellent catalytic properties is obtained when the reduced solids product is treated with very specific proportions of a dialkyl ether having alkyl groups of 4 to 5 carbon atoms and hexachloroethane under very specific treatment conditions. So far as is presently known, there is no prior art which shows the specific process which the inventors have found leads to the production of a titanium trichloride catalyst of such excellent .alpha.-olefin polymerization performance.